(1) Field of the Invention
The present invention relates to turbine disk constructed to minimize the maximum hoop stress experienced across the disk bore. More specifically, the present invention teaches a disk bore contoured so as to increase performance and reduce weight.
(2) Description of Related Art
It is known in the art to fabricate high pressure turbine disks for gas turbine engines, particularly those for aircraft gas turbine engines. With reference to FIG. 1, there is illustrated an exemplary turbine disk known in the art. Disk 11 is shown in cross-section with accompanying centerline 12 about which disk 11 rotates through 360°. Disk 11 is comprised, generally, of a cylindrical disk bore 13 connected to a rim 20 via a web 16. Rim 20 is of a rim width 19. In addition, rim 20 extends away from centerline 12 for a distance extending between live rim radius 15 and dead radius 17. As illustrated in cross-section, disk bore 13 appears as a straight line parallel to centerline 12. When rotated through 360°, disk bore 13 forms the surface of a cylinder extending the width of disk bore 13.
In operation, disk 11 rotates around centerline 12 at high speed. As a result of this rotation, disk bore 13 experiences circumreferential hoop stress. This hoop stress is not constant across the disk bore 13, but, rather, may vary across the width of disk bore 13. In an exemplary instance, the hoop stress experienced at the ends of the disk bore 13 can be 140 KSI with a center disk bore 13 hoop stress of 160 KSI. This results in a hoop stress differential of 20 KSI. The differences arising in the hoop stress present across the disk bore present engineering challenges. Too great a hoop stress differential across disk bore 13 may result in failure of the disk 11 when in operation. It is therefore advantageous to create a disk bore 13 which experiences more uniform hoop stress across disk bore 13 in operation. In other words, it is preferable to minimize the maximum hoop stress differential experienced across disk bore 13.
With reference to FIG. 2, there is illustrated one solution to the problem of minimizing the maximum hoop stress differential experienced across a disk bore 13. Specifically, there is illustrated a dual web disk 11. Dual web disk 11 makes use of two webs 16, 16′ to attach the disk bore 13 to the rim 20. While such an arrangement is quite successful in minimizing the maximum hoop stress differential experienced by the disk bore 13, it presents various difficulties in fabricating a disk 11 of such complexity, and subsequently results in an expensive configuration to fabricate.
What is therefore needed is a simple design similar to the disk 11 illustrated in FIG. 1, which serves to minimize the maximum hoop stress differential in an efficient manner as does the dual web disk 11 of FIG. 2, but which is both simple to fabricate, and therefore relatively cheap to construct.